J/A+A/615/A9 Distribution of Serpens South protostars (Plunkett+, 2018)
Distribution of Serpens South protostars revealed with ALMA.
Plunkett A.L., Fernandez-Lopez M., Arce H., Busquet G., Mardones D.,
Dunham M.M
<Astron. Astrophys. 615, A9 (2018)>
=2018A&A...615A...9P 2018A&A...615A...9P (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; Protostars ; Interferometry
Keywords: stars: formation - stars: protostars - submillimeter: stars -
techniques: interferometric - methods: observational
Abstract:
Clusters are common sites of star formation, whose members display
varying degrees of mass segregation. The cause may be primordial or
dynamical, or a combination both. If mass segregation were to be
observed in a very young protostellar cluster, then the primordial
case can be assumed more likely for that region. We investigated the
masses and spatial distributions of pre-stellar and protostellar
candidates in the young, low-mass star forming region Serpens South,
where active star formation is known to occur along a predominant
filamentary structure. Previous observations used to study these
distributions have been limited by two important observational
factors: (1) sensitivity limits that leave the lowest-mass sources
undetected, or (2) resolution limits that cannot distinguish binaries
and/or cluster members in close proximity. Recent
millimeter-wavelength interferometry observations can now uncover
faint and/or compact sources in order to study a more complete
population of protostars, especially in nearby (D<500pc) clusters.
Here we present ALMA observations of 1mm (Band 6) continuum in a
3x2-arcminutes region at the center of Serpens South. Our angular
resolution of 1-arcsec is equivalent to 400 au, corresponding to
scales of envelopes and/or disks of protostellar sources. We detect 52
sources with 1mm continuum, and we measure masses of
0.002-0.9 solar masses corresponding to gas and dust in the disk
and/or envelope of the protostellar system. For the deeply embedded
(youngest) sources with no IR counterparts, we find evidence of mass
segregation and clustering according to: the Minimum Spanning Tree
method, distribution of projected separations between unique sources,
and concentration of higher-mass sources near to the dense gas at the
cluster center. The mass segregation of the mm sources is likely
primordial rather than dynamical given the young age of this cluster,
compared with segregation time. This is the first case to show this
for mm sources in a low-mass protostellar cluster environment.
Description:
Here we provide the ALMA Band 6 continuum observations of Serpens
South, which are part of the project 2012.1.00769.S, PI: A. Plunkett.
Data obtained with the 12m array and 7m array have been combined in
the uv plane to create these maps. We include two maps, one without
the primary beam (PB) correction and one with the PB correction.
Objects:
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RA (2000) DE Designation(s)
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18 30 03.00 -02 01 58.2 Serpens South = Serpens South Cluster
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 111 67 Sources in mapped region
list.dat 132 2 List of fits images
fits/* . 2 Individual fits images
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See also:
J/ApJ/692/973 : Protostars in Perseus, Serpens and Ophiuchus (Enoch+, 2009)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Name (SerpsNN)
9- 10 I2 h RAh Right ascension (J2000)
12- 13 I2 min RAm Right ascension (J2000)
15- 21 F7.4 s RAs Right ascension (J2000)
23 A1 --- DE- Declination sign (J2000)
24- 25 I2 deg DEd Declination (J2000)
27- 28 I2 arcmin DEm Declination (J2000)
30- 36 F7.4 arcsec DEs Declination (J2000)
38- 40 A3 --- Class Classification
42- 46 F5.2 --- alpha ? Radio spectral index
48- 51 F4.2 arcsec FWHMmaj ? FWHM of major axis (1)
52 A1 --- n_FWHMmaj [ui] Note on FWHMmaj (2)
54- 57 F4.2 arcsec FWHMmin ? FWHM of minor axis (1)
58 A1 --- n_FWHMmin [u] Note on FWHMmin (2)
60- 64 F5.1 deg PA []? Position angle (1)
65 A1 --- n_PA [u] Note on PA (2)
67- 72 F6.2 mJy/beam FPeak ? Peak flux at 1.3mm
75- 80 F6.2 mJy Flux ? Flux density at 1.3mm
82- 86 F5.3 Msun Mass ? Mass
88-103 A16 ---- D15 Source ID for matching source in Dunham et
al. (2015, Cat. J/ApJS/220/11) catalog
104 A1 --- n_D15 [d] Note on D15 (3)
106 A1 --- X [X-] X indicates an X-ray source counterpart
(Getman et al., 2017, Cat. J/ApJS/229/28)
107 A1 --- n_X [g] Note on X (4)
108 A1 --- --- [|]
109-110 I2 --- R ? Specific radio source counterpart labeled
as VLANN by Kern et al.
(2016AJ....151...42K 2016AJ....151...42K)
111 A1 --- n_R [efgh] Note on R (4)
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Note (1): blank indicates no corresponding mm source.
Note (2): Notes as follows:
u = mm source was unresolved
i = Two 2D Gaussian fits were made for sources serps16/18 and serps32/33.
See Sect. 3 for discussion.
Note (3): d: Two continuum sources are located within 2" of the same IR source.
Note (4): Notes as follows:
e = A radio source is located within 4" but anothermm source is closer to the
location of the respective radio source.
f = This mm source is the best match to a radio source, but at least one
other mm source is located within 4" of the same radio source.
g = Tentative match between a mm source a X-ray source within 4". Note that
the distance between this X-ray source and the radio source VLA9 is
actually ∼7", with the mmsource location in between.
h = Tentative match between a mm source and a radio source within 4".
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 51 A22 --- Obs.Date Observation date (2014-03-22T08:59:09.84)
53- 58 F6.2 GHz Freq Observed frequency
60- 63 I4 Kibyte size Size of FITS file
65- 76 A12 --- FileName Name of FITS file, in subdirectory fits
78-132 A55 --- Title Title of the FITS file
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Acknowledgements:
Adele L. Plunkett, aplunket[at]eso.org
History:
03-Jul-2018: on-line fits data
27-Sep-2018: table A1 added from electronic version
(End) Adele L. Plunkett [ESO], Patricia Vannier [CDS] 07-Apr-2018